This invention relates to a turbine stator wheel, in particular to a high-pressure turbine stator wheel of a gas turbine, especially for being used with a gas-turbine engine.
It is known from the state of the art that the stator vanes of a turbine stator wheel in particular must be designed according to aerodynamic requirements. The contouring of the vane cross-section on the suction side and on the pressure side plays a major role here, but also important is the design of the vane passage between adjacent stator vanes, since the available flow cross-section through the passage partly determines the efficiency of the stator wheel.
The aerodynamic design must however take particular account of ensuring the burn-back capability of the stator vanes of the stator wheel. The burn-back capability of the stator wheel must be understood in this connection as the characteristic that during operation of the gas turbine the trailing edge in particular of the first stator wheel of the high-pressure turbine can burn off under the extreme thermal loads occurring. This means that the stator vane, starting from the vane trailing edge, is shortened by the burn-back. Since the first stator wheel of a high-pressure turbine mainly determines the flow rate through the entire turbomachine, maintenance of the flow rate (capacity) of the first stator wheel is of crucial importance so that the entire turbomachine and all individual components can continue to operate with a nominal mass flow at the design point. It is thus necessary that the flow rate (capacity) of the turbine does not substantially change due to the burn-back.
To ensure the burn-back criterion of a turbine stator wheel, the passage cross-section inside the stator wheel upstream of the narrow cross-section (i.e. in the direction of the progressing burn-back of the vane trailing edge) must remain approximately constant, so that even in the case of burn-back of the thermally highly loaded trailing edge, the narrow passage cross-section then effective also remains approximately constant. It is thereby ensured that the flow rate remains similar even in the case of burn-back. An embodiment of this type is known for example from FIG. 4 of DE 10 2005 025 213 A1.
The disadvantage of the stator wheel designs known from the state of the art is that the aerodynamic design cannot be made loss-optimized, since the generally advantageous design with heavy aerodynamic loading in the rear suction-side area (“Rear-Loaded-Design”) greatly infringes the burn-back criterion. It is therefore always necessary to compromise in the aerodynamic design so that the burn-back capability is ensured. This in turn reduces the turbine efficiency and increases the specific fuel consumption (SFC) of the turbomachine.